1. Field of the Invention
The present invention relates to a vehicle lamp including a plurality of light source units constituting a light source by a semiconductor light emitting element. The present invention is particularly preferable for a vehicle lamp including a light distribution control mechanism for changing an irradiating direction or an irradiating range in accordance with a running situation.
2. Related Art
In recent years, high brightness formation of a light emitting element has been progressed, and a vehicle lamp adopting the light emitting element as a light source has been started to develop. However, when a light emitting element is constituted by high brightness formation, also a heat generating amount thereof becomes large, a drawback of reducing a light flux or changing a luminescent color is brought about from a temperature characteristic of the light emitting element. Therefore, in a vehicle lamp for forming a light distribution pattern by a plurality of lamp units constituting a light source by a light emitting element, it is necessary to restrain a temperature rise of the light emitting element (refer to Patent References 1, 2).
For example, as shown by FIG. 22A, there is known an inner heat radiating structure. In the heat radiating structure, a plurality of lamp units 503a, 503b, 503c are integrated by a bracket 505 in a lamp chamber 502 formed by a lamp body 500 and a front face cover 501. Heat in the lamp chamber 502 is radiated by attaching a heat sink 507 to the bracket 505. According to the inner heat radiating structure integrally constituting such a lamp unit, when a light distribution control mechanism of an aiming mechanism, a swivel mechanism or the like is adopted (refer to Patent Reference 3). The bracket 505 integrally fixing the lamp units 503a, 503b, 503c is rotated centering on one rotational center axis.    [Patent Reference 1] JP-A-2004-311224    [Patent Reference 2] JP-A-2004-127782    [Patent Reference 3] JP-A-2005-141918
However, according to the inner heat radiating structure of the background art, a restriction of a vehicle lamp inner volume is considerable and there poses a problem that it is difficult to ensure a space of containing the heat sink having a necessary size compatible with a heat generating amount of the light emitting element. On the other hand, when a heat sink having a sufficient heat radiating area is contained, the heat sink is contrary to a request for light-weighted formation, thin size formation of the vehicle lamp.
Contrary thereto, as a related art which is not a prior art, FIG. 22B shows an outer heat radiating structure achieving a high heat radiating function by arranging only the heat sink 507 provided at the bracket 505 at outside of the lamp body 500.
According to the outer heat radiating structure of the related art, the heat sink 507 is arranged outside, and therefore, in comparison with the inner heat radiating structure of radiating heat radiated at inside of the lamp chamber to outside by way of the lamp body or the like, heat is radiated directly to outer air and a high heat radiating effect is achieved.
However, in order to arrange the heat sink 507 at outside, in order to permit to make an aiming mechanism, a swivel mechanism or the like movable, as shown by FIG. 22C, a gap of making the lamp body 500 and the heat sink 507 movable needs to be sealed in watertight by a socket cover 509 and a complicated seal structure is needed.
In addition, the socket cover 509 constituted by an elastic member of rubber or the like becomes hard when a temperature is low, and therefore, a load of driving a swivel actuator or an auto leveling actuator is increased. In addition thereto, according to a swivel operation of providing a plurality of lamp units at a bracket and making a total of the bracket integrally movable, a movable range at inside of the vehicle lamp becomes large, the lamp chamber needs to be enlarged extraneously by that amount, which is contrary to small-sized/thin size formation of the vehicle lamp.